Annual monitoring of DMS-producing bacteria in Tokyo Bay, Japan, in relation to DMSP

The population of dimethylsulfide (DMS)-producing bacteria together with the DMS and dimethylsulfoniopropionate (DMSP) concentrations were monitored from July 1995 to August 1996 in Tokyo Bay, Japan. The concentration of DMS varied widely in the range from 2 to 130 nM, and the total, dissolved and particulate DMSP concentrations varied from 5 to 220 nM, from below the detection Limit to 75 nM, and from 5 to 200 nM, respectively. The observed particulate DMSP concentration was well explained by the DMSP attributable to Dinophyceae, estimated from the species-specific DMSP per cell contents. The population of DMS-producing bacteria enumerated by the Most Probable Number method was in the range from 1.6 x 10(3) to 9.2 x 10(4) cells ml(-1). A positive relationship was found between the population of DMS-producing bacteria and the total DMSP concentration in some months, suggesting an important role of bacteria in DMS production. However, some other data points showed the small population of DMS-producing bacteria in spite of the high concentrations of DMS and total DMSP. These data did not agree with the above relationship and suggest a contribution of non-bacterial DMS production under certain circumstances.